A Pesticide Information Project of Cooperative Extension Offices of
Cornell University, Michigan State University, Oregon State University, and
University of California at Davis. Major support and funding was provided
by the USDA/Extension Service/National Agricultural Pesticide Impact
Assessment Program.

PesticideInformationProfile

Triadimefon

Publication Date: 5/94

TRADE OR OTHER NAMES

Trade names for products containing triadimefon include Amiral, Bay
MEB 6447, and Bayleton. The compound may also be found in formulations
with other fungicides such as captan, carbendazim, folpet, dodine, and
propineb (1).

REGULATORY STATUS

Triadimefon is a General Use Pesticide (GUP).

INTRODUCTION

Triadimefon is also known as Bayleton. It is a systemic fungicide in
the triazole family of chemicals. Triadimefon is used to control powdery
mildews, rusts and other fungal pests on cereals, fruits vegetables, turf,
shrubs and trees.

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

Triadimefon is a moderately toxic compound that carries the signal
word WARNING on its label. While there is a rather extensive amount of
information on the acute toxicity of the compound to certain animals, there
is very little information about its direct effects on humans.

The technical compound Bayleton (92.6% triadimefon) has an acute oral
LD50 in rats of 569 mg/kg, around 1,000 mg/kg in mice, and about 500 mg/kg
in rabbits and dogs (1). These rather consistent values are slightly
higher than normal for the classification moderately toxic. The compound
is given the stronger classification because of its potential to cause
adverse chronic effects at low to moderate dose levels. As expected, the
lower potency formulations of Bayleton have lower toxicities (higher LD50
values).

Acute inhalation toxicity of the compound is rather low. The
inhalation LC50 is greater than 291 mg/m3 for rats and near that amount for
mice exposed over a four-hour interval (1). Acute toxicity through
exposure to the skin is also fairly low. The LD50 values for the dermal
toxicity of Bayleton (technical) are greater than 1,000 mg/kg for rats and
2,000 mg/kg for rabbits (2).

There was no information about the signs or symptoms of acute
toxicity.

CHRONIC TOXICITY

While there are a number of studies on the chronic toxicity of the
compound to a variety of different species, the main concern is its
potential to cause birth defects.

A number of two year studies have indicated that there are several
toxic responses to low to moderate doses of the compound. Dogs fed
triadimefon over a range of doses exhibited a reduction in body weight, a
decrease in enzyme activity, and an increase in cholesterol levels at the
highest doses tested (2).

Reproductive Effects

Female rats fed up to 90 mg/kg of Bayleton over three generations
showed a number of adverse effects. No effects were noted in the fetuses
at the maternal doses below 2.5 mg/kg. At the middle doses tested (around
15 mg/kg) the second generation offspring experienced a decrease in weight
gain. At the highest dose, the females experienced a reduction in body
weight and a decrease in fertility (2). In another study conducted over
only two generations, the female rats experienced decreases in their ovary
weights at the 2.5 mg/kg dose (2). At 90 mg/kg there were reductions in
litter size and reduced viability of the offspring combined with lower
birth weights for the second generation offspring (2). The evidence
suggests that there is some potential for compound induced effects in
humans though only at moderate to high levels of exposure over time.

Teratogenic Effects

Bayleton's teratogenic potential is relatively low (3). The
concentrations of Bayleton that caused birth defects in rats were high
enough to also produce maternal toxicity. Cleft palates were noted in the
offspring of female rats fed moderate doses of 75 mg/kg (length of time was
not noted). In another study, no teratogenic effects were noted in the
offspring of female rats fed 50 mg/kg of Bayleton in the form of an
emulsion. In another teratogenic study, rib deformities were noted in
offspring when female mother rats were fed the high dose of 90 mg/kg (2).

In response to the compound's potential to produce teratogenic effects
in rats and thus a possibility in pregnant female workers, a study of the
exposure levels of pesticide workers to the compound was conducted. The
study showed that the highest dermal and inhalation level of exposure for
workers was around 60 ug which adds up to approximately 0.008 mg/kg/8-hrs
for a 70 kg worker, which is a value considerably lower than the 10 mg/kg
that caused teratogenic effects in test animals (3). Thus, Bayleton's
potential to present a risk of human birth defects is minimal.

Mutagenic Effects

Six separate studies indicate that the Bayleton compound is non-
mutagenic. Several other tests were inconclusive (2). It is unlikely that
the compound poses a significant mutagenic risk to humans.

Carcinogenic Effects

Two out of three studies on Bayleton's potential to cause cancer were
negative. The highest dose tested in the two negative studies was 250
mg/kg. This dose produced a significant decrease in body weight gain and a
decrease in the red blood cell count and 'violent motor reactions' in the
exposed rats. There was also considerable illness and eventually death at
this relatively high dose. Thus, the study does not adequately conform to
the EPA guidelines for carcinogenicity testing. In the other negative
study, mice were fed moderate doses (90 mg/kg) of Bayleton (technical).
While the test animals experienced decreased body weight gain and a
reduction in red blood cell count and other symptoms of chronic toxicity,
no cancer was detected.

The third study conducted over one year produced cancer related
changes in the liver of the mice at a moderate dietary dose of 90 mg/kg.
There were no other toxic effects noted for the mice at the highest dose
tested (540 mg/kg) (2).

Based on the conflicting evidence presented by the three studies
outlined above, no conclusion can be drawn about the overall
carcinogenicity of triadimefon.

Organ Toxicity

The compound is non-irritating to the skin and the eyes. Moderate
doses (up to 90 mg/kg) of Bayleton have induced a number of different
changes in the liver, decreased kidney weights, and altered urinary bladder
structure (2).

Fate in Humans and Animals

After oral administration of a single dose of Bayleton, most of the
compound was eliminated in the urine and feces unchanged within two to
three days. Some breakdown of a small amount of the compound occurred in
the liver. The compound has a very short residence time in the blood
stream. Half of the initial amount of the compound was removed from the
blood within two and a half hours (1).

When applied to the skin of rats, forty percent of the applied amount
was excreted in urine and feces within eight days. Additional amounts (up
to 40%) were recovered from the skin surface and in the cage (2).

ECOLOGICAL EFFECTS

Effects on Birds

Triadimefon ranges from slightly toxic to practically non-toxic to
birds. For instance, the compound has an LD50 value of greater than 4,000
mg/kg in mallard ducks indicating that the compound has little lethal
effect on the species (1). Japanese quail are less tolerant of the
compound (LD50 of 2,000 mg/kg) and canaries are even less tolerant (LD50 >
1,000 mg/kg) (1). Even the most tolerant species exhibited some compound
related toxicity such as diarrhea and regurgitation within five minutes of
administration of the highest doses (5). At the lowest dose tested (500
mg/kg) no signs of diarrhea were noted.

Effects on Aquatic Organisms

The compound is slightly toxic to fish, indicating that fish are more
susceptible to the presence of the compound than are birds. Bluegill
sunfish are the most susceptible followed closely by goldfish, with LC50
values of 11 mg/l and 10mg/l, respectively. The compound is only slightly
toxic to rainbow trout (LC50 of 14 mg/l) (1). As with some fish species,
Bayleton is moderately toxic to the aquatic invertebrate Daphnia magna, the
water flea. The LC50 of the compound in this species is 1.6 mg/l.

Effects on Other Organisms (Nontarget species)

The compound is non-toxic to honeybees.

ENVIRONMENTAL FATE

Research regarding the behavior and fate of the compound in the
environment is sparse.

Breakdown of Chemical in Soil and Groundwater

In a sandy loam type of soil half of the initial amount of the
compound was lost within eighteen days. In loamy soil the half-life was
much shorter (about 6 days) which indicates that breakdown of the compound
varies with soil type (6).

No information was found about the compound's potential to leach from
soil, or about its potential to accumulate in surface water or groundwater.

Breakdown of Chemical in Surface Water

In water with a pH 3.0, 6.0, or 9.0, almost 95% of the compound
remained after 28 weeks. The compound is very stable in water (6).

Breakdown in Vegetation

No information was available.

PHYSICAL PROPERTIES AND GUIDELINES

Triadimefon consists of colorless crystals. It can also be dry
flowable or wettable powder, or granule or paste.